1. Field of the Invention
The present invention relates generally to packaging of microelectromechanical systems (MEMS) and complementary metal oxide semiconductor (CMOS) devices and, more specifically, to laser processing of glass frit for sealing applications.
2. Description of the Related Art
MEMS and CMOS devices have numerous applications in the areas such as electronics, information processing and projections displays. MEMS and CMOS devices are typically fabricated by bonding a capping layer over an underlying a wafer or substrate bearing active devices (such a wafer or substrate is referred to herein as a “workpiece”). Conventionally, bonding of the capping layer to the workpiece is accomplished utilizing bonding agents requiring a high temperature step.
Glass frit is a well-known bonding agent capable of maintaining a hermetic seal. One approach to packaging MEMS and CMOS devices includes creating an assembly comprising a workpiece, glass frit disposed on top of the workpiece, and a capping layer disposed on top of the glass frit. Subsequently, the assembly is heated to 400° C. or above to induce a glassy transition in the glass frit and to bond the workpiece and the capping layer once the assembly is cooled. One drawback to this approach, however, is that the entire assembly is heated to high temperatures. As a result, some materials may be outgassed, which may contaminate the active devices included on the workpiece. In addition, heating the entire assembly to high temperatures is undesirable for applications involving lubricants, such as for some MEMS devices.
As the foregoing illustrates, there is a need in the art for improved methods of sealing MEMS and CMOS devices.